Been to the bottom myself.
It's a nice, relaxing mini game-esque thing IMHO. You can invest quite a bit of time, get more, or less time if you don't want to put that much.
I get that in older games mines were more needed since there were no crops in winter, and then not really beyond greenhouses in some, but I still miss them.
Then again I think DS has some great things like gold lumber/more free range construction and the crop lv system.
Honestly I can't even think of the latter without it souring the newer crop quality systems.